Process of treating hydrocarbons



NOV. 15, 1932. MOORE 1,887,941

PROCESS OF TREATING HYDROCARBONS Fil ed Jan. 15, 1930 mare-o mam DEF/ LE06/14 7/0 I? FRACUO/VAUM CHE M. 8516167775 FIXED GASES WIPE/i FliACT/O/VPOLYMER; CONTACTED WPOI? 6116b OIL R RE/"L UX ME/K5272! COIVDf/KMT/U/V4ND COOL l/VG F/Ml. HWDMIT 3g)? Patented Nov. 15, 1932 UNITED. STATESPATENT oFFcE a NORMAN H. MOORE, OF WESTFIELD, NEW JERSEY, ASSIGNOR TOTHE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE PROCESSOF TREATING HYDROCARBONS Application filed January 15, 1930. Serial No.421,027.

This invention relates to a process of treating hydrocarbon oils andmore particularly to the treatment of relatively light hydrocarbondistillates, such as cracked naphthas and the like, for the productionof commercial gasoline of low vapor tension and which is free fromundesirable unsaturated constituents.

The invention broadly contemplates a process of treating vapors evolvedfrom the cracking of hydrocarbon oils for the production of gasolinecomprisin dephlegmation of the evolved vapors to form an overhead vaporfraction substantially composed of gaseous constituents, rectifying theresulting vapor fraction to produce a stabilized condensate free fromfixed gases which is to undergo further treatment with subsequentproduction of a vapor fraction of desired final and point and ultimatelycontacting the vapor fraction of final end point with comminuted solidadsorbent catalytic material to effect polymerization of its undesirableunsaturated constituents.

In a preferred embodiment of the invention cracked vapors evolved eitherfrom cracking chambers or from flash or evaporative drums to which thecracked material or synthetic charge oil may be conducted from crackingchambers or heating coils, are subjected to dephlemgation orfractionation, preferabl under superatmospheric pressure derived fromthe cracking system, to produce a naph tha vapor fraction having an endpoint higher than that desired for the final gasoline-product and aliquid fraction or reflux condensate substantially free from thegasoline constituents which is preferably returned to the cracking coilsor reaction drum to undergo further conversion.

The formation of a high end point naphtha vapor fraction during theforegoing fractionation for the subsequent production of an ultimategasoline having a desired end point which is lower than that of thenaphtha fraction is preferable to the direct formation of a vaporfraction having the desired final end point, especially when-theforegoing fractionation or dephlegmation is carried out undersubstantially the same pressure which from the following discussionwhich has refcrating in this manner.

The naphtha vapor fraction which has associated with it an appreciableproportion of volatile products resulting from the crackin reaction andwhich are of thenature of fixed or permanent gases is rectifiedpreferably without prior condensation or cooling and while still undereither superatmospheric or reduced superatmospheric pressure derivedfrom the cracking system in order to remove these undesirable fixedgases which, if not re moved from the naphtha, would escape when thevapor is subsequently condensed to form a distillate at reduced oratmospheric pressure carrying with them valuable naphtha or gasolineconstituents.

The rectified or stabilized naphtha. may be treated with acids, alkalior other suitable chemical reagents for the partial removal ofimpurities such as sulfur compounds or certain unsaturated constituents,4 following which it is re-vaporized and fractionated to form a vaporfraction of desired final end point. 80

The re-fractionated vapor fraction is then subjected to catalytictreatment by contacting with a solid comminuted adsorbent or catalyticmaterial such as for example, fullers earth, charcoal, bone black or thelike to bring about polymerization and subsequent removal of itsunstable and unsaturated constituents.

The invention may be clearly understood erence to the accompanyingdrawing illustrating a flow diagram of the preferred method ofpracticing the invention.

In carrying out the invention the vapors evolved from the conversion ordecomposition of hydrocarbon oils by liquid or vapor phase or combinedliquid and vapor phase cracking which may be under superatmosphericpressures, as for example 400 pounds or even greatly in excess of this,or, on the 10( other hand,' at pressures considerably reduced from thissuch as 50 pounds or even more nearly approaching atmospheric, arepassed to a dephlegmator or fractionator and subjected to fractionationtherein, preferably under pressure derived from the cracking stills orcoils, to produce a low boiling or cracked naphtha vapor fraction and a.high boiling liquid fraction substantiallyfree from naphtha or gasolineconstituents, which liquid may be either withdrawn from the system orpreferably returned to the cracking apparatus for further heating andcracking.

The cracked vapors evolved from the cracking of hydrocarbon oils inconventional cracking coils or reaction chambers or from flash chambersoperating in conjunction therewith may comprise in addition to thedesirable gasoline fractions, a relatively small proportion of fixed orpermanent gases and a relatively large and preponderant proportion ofpartially cracked material having a boiling point considerably higherthan that corresponding to naphtha or gasoline and may, for example,have a distillation end point ranging from 700 F. to 800 F. Thus theevolved vapors may be dephlegmated or fractionated to produce a vaporfraction which has an end point of around 450 F. from which a gasolineproduct having an end point of 400 F., for example, may later be formed,and a liquid condensate or gas oil fraction substantially free fromconstituents boiling below the end point of the vapor fraction formedduring dephlegmation.

The vapor fraction formed in the above mentioned fractionating stepcontains the fixed or permanent gases which, when the vapor is condensedto form a gasoline or naphtha distillate, are held in solution in theliquid under the pressures usually employed during fractionation andcondensation, imparting a high vapor tension to the liquid, and when thepressure is subsequently reduced these gasesare largely released fromthe liquid carrying with them valuable gasoline fractions. Even thoughthe fractiona tion and subsequent condensation may be carried out atpressures approaching atmospheric and the resulting distillate containsa minimum of these fixed gasesthere will still be an appreciable lossdue to the very high vapor pressure of these gases and their carryingeffect as they escape from the distillate and therefore it is desirableto rectify the naphtha vapor, preferably prior to condensation orfurther treatment, to effectively remove these gases in order to preventloss of valuabl gasoline constituents during subsequent treatment aswell as during later transportation and storage.

While the vapor fraction may be condensed and cooled immediatelyfollowing its removal from the deph'legmator to form a naphthadistillate which may be charged to the rectifying apparatus or'may begiven a preliminary chemical treatment for the removal of impuritiesprior to rectification, such as scrubbing with an alkali to removehydrogen sulfide, it is preferable to introduce the vapor fraction tothe rectifier or stabilizer without previous condensation or cooling inorder to take advantage of the sensible heat contained in the vaporwhich may be liberated within the rectifier to effect the necessaryre-vaporization during rectification to remove the fixed gases andthereby minimize, and perhaps entirely eliminate, the quantity of heatto be added from external sources.

Accordingly the vapor fraction formed during the primary fractionationor dephlegmation is subjected to further fractionation or rectificationto produce a rectified or stabilized condensate of desired vaportension. the fixed or permanent gases which were previously dissolvedtherein being removed in a substantially dry state or containing such asmall proportion of normally liquid constituents that it would not bepracticable to further treat the gases for the extraction of gasolineconstituents prior to their disposalas fuel or in any other suitablemanner.

The rectification step is preferably carried out under superatmosphericpressure originally derived from the cracking system which may besubstantially the same pressure prevailing in the cracking system or inthe dephlegmator, although it is contemplated that pressures reducedbelow that prevailing in the cracking vessel or in the dephlegmator mayalso be employed.

Since the cracking reaction is usually carried out under autogenouspressures in excess of atmospheric the subsequent treating stepsincluding fractionation, condensation and rectification are preferablycarried out under pressure originally derived from the cracking system,employing any desirable gradation of pressures throughout theseconsecutive treating steps and thereby avoiding the necessity ofproviding means for positive displacement therethrough of the materialundergoing treatment.

While subsequent treating steps immediatelv following those justmentioned may be sion may be chemically treated with acid,

caustic, or other suitable chemical reagent in order to remove a portionof the impurities contained thereinsuch as sulfur compounds or some ofthe undesirable unsaturated con- Ill stituents prior to the latertreatment with catalytic adsorbent material.

The chemical treatment may beof the nature of a washing with caustic,soda ash or other suitable reagent to remove certain undesirable sulfurcompounds such as mercaptans and hydrogen sulfide. On the other hand thecondensate may be subjected to acid treatment with either weak or strongacid, as may be desired, to effect partial removal of certainunsaturated constituents or other unstable impurities the remainder ofwhich are removed in the later treatment with catalytic material whichwill be fully discussed shortly. While the catalytic material may removeall of these undesired constituents without a prior acid treatment it ispreferable to subject the condensate to such prior acid treatment inorder to insure an ultimate product-of superior quality and chemicalstability as well as to increase the life and efli ciency of a givenbatch of catalytic material.

Upon removal of the acid sludge formed during the treatment with acidthe condensate may then be sweetened with alkali, doctor solution orother suitable reagent.

The chemically'treated stabilized oil which is in liquid form is nowre-vaporized either prior to or in conjunction with the finalfractionation to which it is subjected in order to produce therefrom achemically treated rectified vapor fraction having a desired final endpoint which, as previously explained, is lower than that of the originalvapor fraction formed during the primary dephlegmating or fractionatingstep and a liquid or gas oil fraction free from the desired gasolineconstituents which may be withdrawn to storage or returned to thecracking system for further treatment. a

The stabilized or rectified gasoline fraction while in vapor form isthen passed through a bed or body of comminuted solid absorbentcatalytic material such as fullers earth or the like where, due to theclose physical contact effected between the vapor and the surface of thesolid particles during passage therethrough, a catalytic reaction occurswhereby polymerization of the undesirable unsaturated and unstableconstituents of the vapor which were not removed during the chemicaltreatment is brought about. .In this catalytic reaction the unsaturatedconstituents are polymerized to form liquid compounds or polymers whichhave a higher boiling point than the valuable gasoline components withwhich they we cassociated prior to polymerization. Thus the polymers areseparated from the-treated vapors either durin or immediately followingthe contacting 0 the vapors with the catalyst by liquefaction orfractional condensation and the contacted vapor, free from polymerousmate rial, may thenbe passed to a final condenser following which it maybe subjected to a final sweetening treatment with chemicals such asalkali or doctor solution to produce a final sweetened gasoline.

lVhile the production of a high end point naphtha vapor fraction duringthe primary dephlegmation of the cracked vapors evolved from thecracking system has been discussed it may be desirable in certain casesto fractionate these cracked vapors to produce directly a vapor fractionhaving the same end point as that desired for the final product as, forexample, when cracking certain stocks which may produce gasolinefractions of superior quality and which do not require acid treatment orrigorous catalytic treatment.

Under these conditions the fractionation step immediately prior tocatalytic treatment may be omitted, it being only necessary torevaporize the rectified condensate preparatory to its passage throughthe catalytic mass. However, when a final end point fraction such as theabove is treated with acid, especially strong acid, the end point'may beraised sufficiently, due to the presence of high boiling polymercompounds formed as a result of the polymerization of unsaturatedconstituents by the acid, to necessitate final fractionation prior tocontacting with the catalyst in order to remove these undesirable highboiling compounds.

Thus by means of this invention the cracked vapors evolved inconventional cracking apparatus may be treated to produce a finalgasoline of desired distillation range free from fixed gases or.so-called wild constituents and which is also free from undesirable, un-

stable and unsaturated constituents which if not removed producecolor-forming compounds and tend to form gummy deposits.

While the removal of the fixed or permanent gases during rectificationof the cracked p vapor has been discussed, the invention furthercontemplates the possibility of removing in addition low boilingfractions relatively heavier than the fixed gases in order to produce arectified condensate having a high initial boiling point, the quantityof such light constituents removed depending upon the desireddistillation range of the final product.

Furthermore while substantially atmospheric pressure is usually employedduring re-vaporization, final fractionation and subsequent contactingwith catalytic material, it is contemplated that either sub-atmosphericor super-atmospheric pressures may be employed during these steps.

Obviously many modifications and variations of the invention, as hereinset forth, may be made Without departing from the spirit and scopethereof. and therefore only such limitations should be imposed as areindicated in the appended claims.

- I claim: 1. In the method of'treating hydrocarbon vapors evolvedduring cracking under superatmospheric pressure, the steps whichcomprise subjecting the evolved vapors to dephlegmation undersuperatmospheric pressure to form a reflux condensate and an overheadvapor fraction'huving an end point higher than that desired for thefinal product, condensing the vapor fraction to form a dis tillate,subjecting the distillate to preliminary chemical treatment for partialremoval of impurities, subjecting the treated distillate torectification under reduced superatmospheric pressure to form acondensate of desired vapor tension, chemically treating the rectifiedcondensate for further removal of impurities, re-vaporizing thechemically treated condensate, fractionating the revaporized condensateto form a vapor of desired final end point and a liquid free fromconstituentsdesiredfor the final product, contacting said vapor withsolid adsorbent catalytic material to polymerize its undesirableunsaturated Constituents and separating and condensing the remainingvapors to form a treated final product.

2. In the method of treating hydrocarbon vapors evolved during cracking,the steps which comprise subjecting the evolved vapors to dephlegmationunder superatmospheric pressure to form a reflux condensate and anoverhead vapor fraction having an end point higher than that desired forthe final product, condensing the vapor fraction to form a distillate,subjecting the'distillate to preliminary chemical treatment for partialremoval of impurities subjecting the partially treated distillate torectification to remove fixed gases and form a condensate of desiredvapor tension, chemically treating the rectified condensate for thepartial removal of impurities, revaporizing the partially refinedcondensate, fractionating the re-vaporized condensate to form a vapor ofdesired final end point and a liquid free from constituents desired forthe final product, contacting said vapor with solid adsorbent catalyticmaterial to polymerize its undesirable unsaturated constituents andseparating and condensing the remaining vapors to form a treated finalproduct.

3. In the method of treating hydrocarbon vapors evolved during cracking,the steps which comprise subjecting the evolved vapors to dephlegmationto form a reflux condensate and an overhead vapor fraction having an endpoint higher than that desired for the final product, condensing thevapor fraction to form a distillate, subjecting the distillate torectification to remove fired gases and form a condensate of desiredvapor tension, acid treating the rectified condensate for the partialremoval of impurities, re-vaporizing the partially refined condensate,fractionatingthe re-vaporized condensate to form a vapor of desiredfinal end point and a liquid free from constituents desired for thefinal prod- 5 net, contacting said vapor with solid adsorbent catalyticmaterial to polymerize its undesirable unsaturated constituents andseparating and condensing the remaining vapors to form a treated finalproduct.

4. In the method of treating hydrocarbon vapors evolved during crackingunder superatmospheric pressure, the steps which comprise subjecting theevolved vapors to fractionation under superatmospheric pressure to forma reflux condensate and an overhead vapor fraction of desired final endpoint, condensing the vapor fraction to form a distillate, subjectingthe distillate to preliminary chemical treatment for partial removal ofimpurities, rectifying the distillate under reduced superatmosphericpressure to form a condensate of desired vapor tension, chemicallytreating the rectified condensate for further removal of impurities,re-vaporizing the partially refined condensate, contacting the resultantvapor with solid adsorbent catalytic material to polymerize itsundesirable unsaturated constituents and separating and condensing theremaining vapors to form a treated final product.

5. In the method of treating hydrocarbon vapors evolved durin cracking,the steps which comprise subjecting the evolved vapors to fractionationto form a reflux condensate and an overhead vapor fraction of desiredfinal end point, condensing the vapor fraction to form a distillate,subjecting the distillate t6 preliminary chemical treatment for partialremoval of impurities, rectifying the partially treated distillate toremove fixed gases and form a condensate of desired vapor tension,chemically treating the rectified condensate for the partial removal ofimpurities, re-vaporizing the partially refined condensate, contactingthe resultant vapor with solid adsorbent catalytic material topolymerize its undesirable unsaturated constituents and separating andcondensing the remaining vapors to form a treated final product.

6. In the method of treating hydrocarbon vapors evolved during cracking,the steps which comprise subjecting the evolved vapors to fractionationto form a reflux condensate and an overhead vapor fraction of desiredfinal end point, condensing the vapor fraction to form a distillate,rectifying .thedistillate to remove fixed gases and form a condensate ofdesired vapor tension, acid treating the rectified condensate for thepartial removal of impurities, re-vaporizing the partially refinedcondensate contacting the resultant vapor with solid adsorbent catalyticmaterial to polymerize its undesirable unsaturated .constituents andseparating and condensing the remaining vapors to form :1 treated finalproduct.

In witness whereof I have hereunto set my hand this 6th day of January,1930.

.NORMAN H. MOORE.

